Structural and functional analysis of SMO-1, the SUMO homolog in Caenorhabditis elegans

PLoS One. 2017 Oct 18;12(10):e0186622. doi: 10.1371/journal.pone.0186622. eCollection 2017.


SUMO proteins are important post-translational modifiers involved in multiple cellular pathways in eukaryotes, especially during the different developmental stages in multicellular organisms. The nematode C. elegans is a well known model system for studying metazoan development and has a single SUMO homolog, SMO-1. Interestingly, SMO-1 modification is linked to embryogenesis and development in the nematode. However, high-resolution information about SMO-1 and the mechanism of its conjugation is lacking. In this work, we report the high-resolution three dimensional structure of SMO-1 solved by NMR spectroscopy. SMO-1 has flexible N-terminal and C-terminal tails on either side of a rigid beta-grasp folded core. While the sequence of SMO-1 is more similar to SUMO1, the electrostatic surface features of SMO-1 resemble more with SUMO2/3. SMO-1 can bind to typical SUMO Interacting Motifs (SIMs). SMO-1 can also conjugate to a typical SUMOylation consensus site as well as to its natural substrate HMR-1. Poly-SMO-1 chains were observed in-vitro even though SMO-1 lacks any consensus SUMOylation site. Typical deSUMOylation enzymes like Senp2 can cleave the poly-SMO-1 chains. Despite being a single gene, the SMO-1 structure allows it to function in a large repertoire of signaling pathways involving SUMO in C. elegans. Structural and functional features of SMO-1 studies described here will be useful to understand its role in development.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cadherins / metabolism
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / chemistry*
  • Caenorhabditis elegans Proteins / metabolism*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • SUMO-1 Protein / chemistry
  • SUMO-1 Protein / metabolism*
  • Sequence Homology, Amino Acid*
  • Solutions
  • Static Electricity
  • Sumoylation
  • Time Factors


  • Cadherins
  • Caenorhabditis elegans Proteins
  • SUMO-1 Protein
  • Solutions

Grants and funding

This work was funded by the Tata Institute of Fundamental Research, Government of India. Ranabir Das acknowledges the DBT-Ramalingaswamy fellowship (BT/HRD/23/02/2006). Parag Surana is supported by Research Associate Fellowship from the Department of Biotechnology (DBT), India. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.